Method of dispersing inorganic oxide sols



Feb. 28, 1956 M, J. MURRAY ET AL 2,736,713

METHOD OF DISPERSING INORGANIC OXIDE SOLS Filed Sept. 2, 1952 INVENTORSIMAURICE J. MURRAY DONALD L. HOLDEN BY; 2' ,z'

Wow/MW AT TO R N EYSZ United States Patent METHOD OF DISPERSINGINORGANIC OXIDE SOLS Maurice J. Murray, Naperville, and Donald L.Holden,

Riverside, [1]., assignors to Universal Oil Products Company, Chicago,Ill., a corporation of Delaware Application September 2, 1952, SerialNo. 307,454 Claims. (Cl. 252-448) This invention relates to an improvedmethod of dispersing inorganic oxide sols in the process for forminginorganic oxide spheres.

In particular, this invention relates to a method for preventing thepremature gelation of inorganic oxide sols, thereby eliminating cloggingof the dispersing device used to disperse the sol.

The petroleum industry has long used catalysts to aid in convertinghydrocarbons to more desirable forms. In particular, catalytic crackingof gas oils has become important and consequently methods of preparing acatalyst have become important in that cracking units ordinarily consumeseveral tons of catalyst per day. Synthetic catalysts are prepared in anumber of ways such as by separately, successively, or coprecipitatingthe components into any convenient shape, after which the catalyst isground to the desired size, or in a preferred method,

the catalyst is formed into spheres.

Spherical catalysts are far superior to other types in that the regularunbroken surface of each individual sphere inhibits the formation offines and thus reduces catalyst losses in fluidized operations.Spherical catalysts are also extremely hard and therefore resistattrition which further reduces catalyst losses and also reduces erosionof plant equipment.

Generally, spherical catalyst is prepared by dispersing a pre-mixed solas small individual particles into a gelling medium, the particlesassuming a spherical shape as they descend through the gelling mediumand setting to a firm gel while in transit through the gelling medium,thereafter being collected as individual firm spheroids. The gellingmedium can be a hot basic gas, such as ammonia, methyl amine etc., orfor basic sols a hot acid gas, such as hydrogen chloride, sulfurdioxide, carbon dioxide, etc., or a hot liquid that is substantiallyimmiscible with the sol such as kerosene, gas oil, Nujol etc. The gelspheroids are collected in a receiver containing a hot aqueous liquidsuch as water in equilibrium with the gelling medium, or aqueoussolutions of electrolytes such as ammonium hydroxide, ammoniumcarbonate, acetic acid etc. The spheroids can also be collected in a dryreceiver or on a conveyer that continuously removes them from thereceiver. In processes in which hot gases are used as the gellingmedium, the dispersing device is by necessity maintained in the gellingmedium since the gelling medium is contained in an enclosure which mustbe sealed in order to prevent the escape of the gelling medium. As aresult of this condition it is characteristic of sphere formingprocesses that the dispersing device is periodically clogged with gelledsol. As the sol passes through the dispersing device some portion of thesol is retained mometarily along the edge or some other relativelystagnant portion of the stream, and, while there retained in thepresence of the gelling medium, the viscosity of this portion of the solincreases, thereby preventing the sol from disengaging from thedispersing device. As a result the retained portion of the sol gelscompletely to a hard mass and remains on the dispersing device,eventually building up to such extent as to hamper the successfuloperation of the disper'sing device.

It is therefore an object of this invention to prevent the prematuregelation of an inorganic sol by maintaining the dispersing device in amedium that retards gelation.

In one embodiment the present invention provides for a means ofmaintaining an atmosphere of acid gas around a device for dispersing anacid sol into a basic gas medium, thereby preventing the prematuregelation of the acid sol. Suitable acidic gel-retarding gases are sulfurdioxide, carbon dioxide and hydrogen chloride.

In another embodiment the present invention provides for maintaining anatmosphere of basic gas around a device for dispersing a basic sol intoan acid gas medium, thereby'retarding the gelation and preventing thepremature gelation of the basic sol. Suitable basic gel-retarding gasesare ammonia and methyl amine.

The gas medium around the dropping device is extremely local, therebycausing a blanketing effect which is only in the immediate vicinity ofthe dropping device. The introduction of this small amount of gas has noeffect on the overall process since the gelation of the sol is retardedonly for the very short time that the sol is in the immediate vicinityof the dropping device.

The method of this invention will be used primarily to produce acracking catalyst for use in converting hydrocarbons from higher boilingfractions to lower boiling fractions by contacting the hydrocarbon withthe catalyst of this invention at a temperature of about from 600 F. toabout 1200 F. or more, and at a pressure of from atmospheric to about1500 p. s. i. or more. Although the catalyst will be used primarily forcracking it may also be used for other reactions such as: l. Processesknown as reforming, isoforming, retreating etc. 2. Polymerizationof'lowboiling hydrocarbons to form higher boiling hydrocarbons. 3. Alkyltransfer reactions as for example, reaction of benzene and ethyl benzeneto form toluene. 4. Treating of hydrocarbon fractions to removeimpurities as for example desulfurization of gasoline. These catalystshave also proved effective in reactions of organic compounds such as thedehydration of alcohols, synthesis of esters, alcohols, and acids etc.

The method of this invention will apply equally well to all of thecommonly used dropping devices such as spray nozzles, rotating discs,serrated cones, etc. This method will also apply to any gelable sol suchas silica sol, alumina sol, zirconia sol, magnesia sol, etc., orcombinations thereof. This method further will apply to sols containingsalts or other electrolytes or particles either in solution or insuspension, such as soluble salts of aluminum, magnesium, zirconium,vanadium, chromium, tantalum and others or the oxides of the metals ofthe above mentioned salts contained in the sol as a suspension. Atypical catalyst is a silica base catalyst containing aluminum inamounts of from about 5% to about 40% made by adding aluminum sol orsalt to a mixture of dilute water glass and sulfuric acid.

Our invention can best be explained with reference to the accompanyingdrawing which illustrates one embodiment of this invention.

Referring now to the figure, the sol is introduced into line 1 throughcontrol valve 2, whereafter it passes through spray nozzle 3, wherefromit is dispersed as small droplets into column 4. The upper portion 9 ofcolumn 4 is laterally contracted to a conical shape so that the droppingnozzle is confined in a relatively small volume. Lines 5 and 7 disposedimmediately opposite of each other entering section 9 and openingadjacent to nozzle 3 are provided for the entry of a gelation retardinggas. Valves 8 and 6 control the flow of the gelation retarding gas. Ascan be seen from the drawing the stream of gelation retarding gasdischarging from lines 5 and 7 meet immediately below the spray nozzle,whereby creating a turbulent zone saturated with gelation retardinggases in the vicinity of the dropping nozzle. The limited volume ofconical section prevents the diffusion of the gellation retarding gasinto the major portion of the column by reducing the quantity ofgelation retarding gas required. In the upper portion of conical section9, line 10 and the control valve 11 are provided to exhaust gelationretarding gas from the column. It is contemplated that the column shalloperate at a slight positive pressure, therefore a continuous exhaust ofgelation retarding gas controlled by a pressure control device will keepthe gelation retarding gas in the upper section of column 4.

In a specific embodiment of the invention as applied to the manufactureof silica spheres, a silica sol is prepared by adding dilute Water glassto a sulfuric acid solution. The resultant sol is passed through spraynozzle 3, emerging therefrom as finely divided particles which pass intoan atmosphere of hot ammonia gas in column 4. Sulfur dioxide gas isintroduced through lines 5 and 7 to maintain the space immediatelysurrounding nozzle 3 in an atmosphere of S02 gas, thereby preventingclogging of the spray nozzle by retarding the premature gelation of thesilica sol.

The drawing is not intended to limit this invention. Many modificationsof the apparatus as herein described may be made within the broad scopeof this invention, as, for example, (1) the use of additional inletconduits for gelation retarding gas, (2) other suitable shapes for thetop closure of column 4 described herein as conical section 9, (3)dropping devices other than a spray nozzle, (4) the use of a hot liquidinstead of a hot gaseous medium for gelation, in which case a topclosure is not necessary on the column although a gas blanket around thedropping nozzle will be provided.

We claim as our invention:

1. In the manufacture of inorganic oxide spheres Wherein a gelablehydrous inorganic oxide sol is dispersed in droplet form through adispersing device in the upper portion of a gelation zone containing agelling medium through which the sol droplets descend and set to a gelduring their descent through said medium, the method of preventingpremature gelation of the sol and resultant clogging of the dispersingdevice which comprises introdueing a gel-retarding gas to the upperportion of said zone in the immediate vicinity of the dispersing deviceand maintaining a localized blanket of said gas around said device.

2. The method of claim 1 further characterized in that said sol and saidgas are acidic.

3. The method of claim 2 further characterized in that said gascomprises sulfur dioxide.

4. The method of claim 2 further characterized in that said gascomprises carbon dioxide.

5. The method of claim 2 further characterized in that said gascomprises hydrogen chloride.

6. The method of claim 1 further characterized in that said sol and saidgas are basic.

7. The method of claim 6 further characterized in that said gascomprises ammonia.

8. The method of claim 6 further characterized in that said gascomprises methyl amine.

9. In the manufacture of silica spheres wherein a silica sol isdispersed in droplet form through a dispersing device in the upperportion of a gelation zone containing an atmosphere of a basic gas inwhich the sol droplets set to a gel, the method of preventing prematuregela'tion of the silica sol and resultant clogging of the dispersingdevice which comprises introducing an acidic gel-retarding gas to theupper portion of said zone in the immediate vicinity of the dispersingdevice and maintaining a localized blanket of said acidic gas aroundsaid device.

10. The method of claim 9 further characterized in that said basic. gascomprises ammonia and said acidic gas comprises sulfur dioxide.

References Cited in the file of this patent UNITED STATES PATENTS1,843,576 McClure et al. Feb. 2, 1932 2,419,272 Marisic et al Apr. 22,1947 2,456,268 Gibbs et a1. Dec. 14, 1948 2,453,084 Brown Nov. 2, 19482,543,132 Shabaker Feb. 27, 1951 2,641,583 Gring June 9, 1953

1. IN THE MANUFACTURE OF INORGANIC OXIDE SPHERES WHEREIN A GELABLE HYDROUS INORGANIC OXIDE SOL IS DISPERSED IN DROPLET FORM THROUGH A DISPERSING DEVICE IN THE UPPER PORTION OF A GELATION ZONE CONTAINING A GELLING MEDIUM THROUGH WHICH THE SOL DROPLETS DESCEND AND SET TO A GEL DURING THEIR DESCENT THROUGH SAID MEDIUM, THE METHOD OF PREVENTING PREMATURE GELATION OF THE SOL AND RESULTANT CLOGGING OF THE DISPERSING DEVICE WHICH COMPRISES INTRODUCING A GEL-RETARDING GAS TO THE UPPER PORTION OF SAID ZONE IN THE IMMEDIATE VINCINITY OF THE DISPERSING DEVICE 